The art is replete with systems for enabling the portable battery powering of consumer and other products of the above-mentioned types, using non-rechargeable replaceable batteries such as so-called alkaline cells and/or rechargeable cells such as nickel-cadmium (NICAD) cells and the like.
It has earlier been proposed, as an illustration, to keep rechargeable batteries charged from the mains power outlet plugs as in U.S. Pat. No. 4,434,509. There are also proposals extending over several decades for using solar cells either directly or in combination with rechargeable batteries, as described, for example in U.S. Pat. Nos. 2,919,353; 2,951,163; 4,122,396; D256,360; and 4,209,346. It has further been proposed to power a radio with the combination of a solar cell, a rechargeable battery and a non-rechargeable battery with means for switching therebetween, as in U.S. Pat. No. 4,667,142; and various ether circuits have been proposed for solar-battery systems including U.S. Pat. No. 3,921,049 for using blocking diodes to prevent the discharge of a battery through a solar cell, and the like.
It is rather significant that, to date, the widespread use of solar cells in such portable battery-operated products has not been achieved, despite the potentially free use of the sun and lighting in home, office and other institutional and public facilities. It is believed that, among the reasons for such lack of general adoption, are the inefficient use of costly solar cells and the lack of adequate energy conservation in the power circuits.
Underlying the present invention, however, is the discovery, of a novel multiple power source system involving solar cells for battery-operated commercial and/or industrial products that can provide for a remarkable degree of energy conservation and, indeed, the insurance of a useful life that can in many cases extend substantially for the life of the product itself or a substantial portion thereof.